Known in the prior art ( SU, A, No. 848201) is a machine tool for finish-machining of bevel gear wheels with circular teeth. The machine tool comprises a tool head with a mechanism for hypoid offset of the tool spindle, and a work head carrying a spindle on which is mounted a carriage with an additional spindle, capable of being offset on a hypoid principle relative to the rotation axis of the work head, and a work generating mechanism. To ensure synchronous rotation of the tool and work, the carriage mounts a summation mechanism. The hypoid distance of the work is set by an eccentric mechanism. However, the provision of a large number of degrees of freedom of the work spindle, an additional spindle with an additional hypoid offset relative to the main spindle of the work head, and a generating mechanism, all this imparts the rigidity of the machine tool and, consequently, the accuracy of machining. Besides, the summation mechanism which synchronizes rotation of both spindles fails to ensure a strictly coordinated rotation of the work and tool within the entire range of the generating motion which introduces additional errors into the machining accuracy.
There is known another machine tool (DE, A I, No. 3 506 499) for precision machining of gear wheels. In this machine tool the tool and the work make up a pair of bevel gear wheels, each installed on one end of its spindle. The other end of each spindle is mounted with one helical spur guiding wheel, both constituting a screw pair. The guiding wheels are arranged coaxially with the tool and work and have the same speed ratio as the tool-and-work pair. Such a design of the machine tool ensuring kinematic interaction between the spindles of the work and tool and their working feed during machining limits the possibilty of selecting the geometrical dimensions of the toothed tool since each particular speed ratio of the tool-and-work gear pair calls for making a set of guiding wheels with the same speed ratio. When the function of the guiding wheels are fulfilled by a bevel gear pair, the working feed setting mechanism complicates the design of the machine tool to such an extent that the maximum rigidity of the machine tool cannot guarantee the high quality machining of precision gear wheels. And the manufacture of a tool in the form of an abrasive toothed wheel on this machine without additional mechanisms is possible.
The closet in its essence to the disclosed machine tool is the machine tool (SU, A No. 671950) for finish machining of bevel and hypoid gear wheels wherein the work and tool spindles are provided with drives electrically linked with each other for kinematic interaction. The speed ratio of the work-and-tool gear pair is ensures by the change gears of the indexing quadrant fitted on the tool spindle. The machine tool has no mechanism for the working feed required for making the toothed abrasive tool. When the function of the working feed mechanism is fulfilled by the setting-up mechanism of the head of one of the spindles, one cycle of this machine tool enables making a toothed abrasive tool for machining only one element of a gear pair. When making the tool for the other element of the pair it is necessary to change the tool settings, i.e. the ratio of the work and spindle speeds, the base distance of the tool and work, etc. The same disadvantage exists when this machine tool is used for finish machining of gear wheels.